Ulysses Grant was his country's greatest general since George Washington. Like Washington, Grant's battlefield performance was the only factor standing between the United States continuing as one, indivisible nation. Grant was the keystone of Union victory, a man whose removal would have resulted in the Union cause crumbling into defeat - and the United States dissolving into a collection of competing sovereign states. It was not always so clear cut. An early military career had ended with his resignation for alleged drunkenness, while in civilian life a number of his business ventures foundered leading to the nickname ''Useless'' Grant. However, victory had its rewards and in March 1864 Grant was promoted to lieutenant-general, the only United States Army officer except for George Washington and Winfield Scott to achieve that rank. By the end of the war Grant would become the United States Army's first full general since Washington.